【摘要】：近幾十年來,藍藻水華已成為世界范圍內一個重點關注的問題。目前,大量的研究工作都集中在營養(yǎng)鹽對水華暴發(fā)的作用機理、藻華的潛在危害以及藻華的控制方法等方面,而關于藻華對營養(yǎng)鹽的反作用機制的研究甚少。因此,本研究在太湖北岸進行藍藻培養(yǎng)試驗,考察藻華暴發(fā)體系對外源輸入硝氮、氨氮的響應,結合分子生物學方法,對藻類所吸收氮素的最終去向進行探索。實驗結果如下:1.添加外源硝氮體系中,含藻水樣中的總氮濃度減少了 3.62mgL-1,其中總有機氮占40%,說明圍隔中存在一種氮素轉化并脫除的機制。硝氮等理化性質的變化表明藻附生菌和游離細菌的耦合礦化作用和硝化反硝化作用是有機氮脫除的主要方式,藻-菌系統(tǒng)減小了氮素在湖泊水體的循環(huán)路徑。因此,藍藻水華可以加速脫氮效率,這可能是夏季太湖中氮素濃度較低的原因。2.添加外源氨氮體系中,在藻類生長初期,藻類在與附生菌對銨的競爭中處于優(yōu)勢地位,但是到藻華中后期,附生菌逐漸占據優(yōu)勢。硝酸鹽氮在夜間的濃度總是高于當天或次日早晨時的濃度,說明白天銨態(tài)氮轉化為硝態(tài)氮,而夜間硝態(tài)氮又逐漸減少。當銨態(tài)氮被進一步消耗,圍隔內部再礦化作用成為耦合硝化反硝化的氮源,導致前期被同化的氮素被有效去除。實驗期間,含藻水樣與空白水樣中的硝酸鹽氮濃度無顯著差異(P0.01),這說明夏季在太湖許多藍藻生物量相對較低的區(qū)域中也能發(fā)生附生耦合硝化反硝化作用,因此,礦化-硝化-反硝化過程可能是夏季太湖低濃度硝酸鹽氮濃度條件下發(fā)生強烈反硝化反應的原因。3.未添加外源氮素體系中,含藻水樣中溶解性有機碳濃度不斷增加并于15日達到峰值72.0 mgL-1,高于太湖原位水背景值12.5倍,而水樣熒光光譜所呈現的4個熒光峰中有3個熒光峰的強度均與葉綠素呈顯著相關(P0.01),表明藻華暴發(fā)中后期藍藻的生長代謝過程及死亡分解過程所釋放的有色可溶性有機質是水體中溶解性有機質的一個重要來源。紫外光譜E3/E4在試驗前中期均大于3.5,在試驗末期有減小趨勢,這說明藻華暴發(fā)初期和中期水體水質腐殖化程度較低。
[Abstract]:In recent decades, cyanobacteria Shui Hua has become a worldwide focus of attention. At present, a great deal of research work has focused on the mechanism of the effect of nutrient salts on Shui Hua outbreak, the potential harm of algal blooms and the control methods of algal blooms, but there is little research on the reaction mechanism of algal blooms to nutrient salts. Therefore, the experiment of cyanobacteria culture was carried out on the north shore of Taihu Lake. The response of algal blooming outbreak system to exogenous nitrate and ammonia nitrogen was investigated, and the final fate of nitrogen absorbed by algae was explored in combination with molecular biological methods. The experimental results are as follows: 1. The total nitrogen concentration in algal water decreased by 3.62 mg / L, and the total organic nitrogen accounted for 40%, which indicated that there was a mechanism of nitrogen transformation and removal in the enclosure. The changes of physicochemical properties such as nitrate and nitrogen showed that the coupling mineralization of epiphytic bacteria and free bacteria and nitrification and denitrification were the main ways to remove organic nitrogen. The algal-bacteria system reduced the circulation path of nitrogen in lake water. Therefore, cyanobacteria Shui Hua can accelerate nitrogen removal efficiency, which may be the reason for low nitrogen concentration in Taihu Lake in summer. 2. In the initial stage of algal growth, algae was dominant in the competition for ammonium with epiphytic bacteria, but at the middle and late stage of algal blooming, epiphytic bacteria gradually occupied the dominant position in the addition of exogenous ammonia-nitrogen system. The concentration of nitrate nitrogen in the night was always higher than that in the same day or the next morning, indicating that during the day the ammonium nitrogen was converted into nitrate nitrogen, but the nocturnal nitrate nitrogen gradually decreased. When ammonium nitrogen is consumed further, the internal mineralization of the enclosure becomes the nitrogen source of coupled nitrification and denitrification, which leads to the removal of nitrogen assimilated in the early stage. During the experiment, there was no significant difference in nitrate nitrogen concentration between the algae-containing water sample and the blank water sample (P0.01), which indicated that the epiphytic coupling nitrification and denitrification could also take place in many areas of Taihu Lake where the biomass of cyanobacteria was relatively low in summer. Mineralization-nitrification-denitrification process may be the reason of strong denitrification reaction at low nitrate concentration in Taihu Lake in summer. In the absence of exogenous nitrogen, the concentration of dissolved organic carbon in algae water increased continuously and reached a peak value of 72.0 mgL-1, on the 15th, which was 12. 5 times higher than the background value of in situ water of Taihu Lake. However, the intensity of three of the four fluorescence peaks in water samples was significantly correlated with chlorophyll (P0.01). The results showed that the dissolvable organic matter released from the growth and metabolism of cyanobacteria during the middle and late stage of algal blooming outbreak and the process of death decomposition was an important source of dissolved organic matter in water. UV spectrum E3/E4 was higher than 3.5 in the first and middle stages of the experiment, and decreased at the end of the experiment, which indicated that the water quality humification degree was lower in the early and middle period of algal blooms outbreak.
【學位授予單位】：揚州大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：X524

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